Conjugated copolymers for use in luminescent devices

ABSTRACT

A process for the preparation of a conjugated poly(arylene vinylene) copolymer for use in a luminescent device, which comprises: (1) providing a precursor polymer comprising units of general formula                    
     in which Ar is substituted or unsubstituted arylene, L is a leaving group, R 1  and R 2  are each independently H, alkyl, alkoxy, aryl or an electron-withdrawing group, and n is an integer; (2) reacting the precursor polymer with a reactant comprising a carboxylate, an aldehyde, a ketone, a sulphonate, a thioate, a disulphide, a xanthate, an amine, a pyridine, a hydrazide, a phenoxide, an alcohol with a boiling point above 100° C., or a derivative thereof, under substitution conditions whereby a proportion of the leaving groups are substituted to form a substituted precursor copolymer comprising units of general formula                    
     in which Ar, R 1 , R 2  and L are defined above, X is a substituent group from the reactant, l and m are independently integers; and (3) converting the substituted precursor copolymer to a conjungated poly(arylene vinylene) copolymer by elimination of the leaving groups from the substituted precursor copolymer.

FIELD OF THE INVENTION

This invention relates to conjugated polymers for use in luminescentdevices, especially electroluminescent devices, and their synthesis.

BACKGROUND TO THE INVENTION

Conjugated polymers have been used as organic electroluminescent (EL)materials in suitable device structures, as demonstrated in our earlierpatent herein incorporated by reference as U.S. Pat. No. 5,399,502.Poly(p-phenylene vinylene) is one such polymer and may be prepared viathe Wessling precursor method as described in, for example “PrecursorRoute to Poly(p-phenylene vinylene): Polymer Characterisation andControl of Electronic Properties” D. D. C. Bradley, J. Phys. D. 20, 1389(1987). For example, a tetrahydrothiophene-based precursor with a halidecounter-ion is typically used as shown in FIG. 1. It has been proposedthat the polymerisation of the p-xylenebis(sulphonium halide) monomeroccurs via a quinoid intermediate as described in “The Polymerisation ofXylylene Bisdialkyl Sulfonium Salts” R. A. Wessling, J. Pol. Sci. Pol.Symp. 72, 55-66, (1985). The conjugated polymer formed is insoluble andintractable and therefore the solution processable precursor isrequired. Device fabrication is carried out using the precursor materialand the conjugated polymer is prepared in situ via a thermal conversionstep. Typically, the precursor polymer is coated, by spin-coating orblade coating or other coating techniques, onto a transparent conductiveoxide layer, for example Indium Tin Oxide (ITO). The ITO is itselfcoated onto a suitable substrate which may be, for example, glass orplastic. The precursor polymer film is then converted on the ITO bysuitable heat treatment. Following this, appropriate metal electrodesare deposited. A multi-layer structure is therefore obtained whichconsists of an anode, the conjugated polymer, and the cathode. Injectionof positive and negative charge carriers at the anode and cathoderespectively leads to light emission. Other layers may be included intothe device to facilitate charge injection/accumulation or to affordprotection during the conversion process. This is shown in FIG. 2.

The advantages of using precursor conjugated polymers as emissive layersin EL devices include:

a) ease of fabrication,

b) amenable to multilayer structures,

c) intractability of converted polymer film, and

d) intrinsic luminescence properties.

However, there is some evidence that the quantum yield for radiativedecay of the excited states is lowered through their migration tonon-radiative decay centres hence photoluminescence and thereforeelectroluminescence efficiencies are significantly reduced. Our previouspatent , herein incorporated by reference as U.S. Pat. No. 5,401,827 hasdealt with this issue by describing a semiconductive conjugatedcopolymer comprising at least two chemically different repeat units withdifferent semiconductor band gaps (for example conjugated andnon-conjugated segments). The optical properties of the copolymer aretherefore determined by the relative proportions of the different repeatunits. Copolymers were prepared in this work either by copolymerisationof more than one bis(sulphonium) salt, control of the degree ofconversion of the precursor polymer, or by the substitution of the THTunit to provide groups that would survive the conversion process. Thelatter approach is shown in FIG. 3 and will henceforth be referred to asthe Substitution Approach.

We now have evidence that conversion of precursor homopolymer orcopolymer systems on certain conductive oxide substrates such as ITO,can lead to undesirable interactions that give rise to either quenchingof luminescence or to modification of the expected copolymercomposition. Furthermore, we have observed that the presence of certainfunctional groups in the copolymer can be detrimental to deviceperformance, and in particular to device lifetime.

SUMMARY OF THE INVENTION

The present invention seeks to provide conjugated arylene vinylenecopolymer systems prepared via the precursor approach as emissive layersin EL devices which overcome these difficulties and retain the benefitof enhanced photoluminescence and electroluminescence efficiency.

The present invention provides a process for the preparation of aconjugated poly(arylene vinylene) copolymer for use in a luminescentdevice, which comprises:

(1) providing a precursor polymer comprising units of general formula

in which Ar is substituted or unsubstituted arylene, L is a leavinggroup, R¹ and R² are each independently H, alkyl, alkoxy, aryl or anelectron-withdrawing group, and n is an integer;

(2) reacting the precursor polymer with a reactant comprising acarboxylate, an aldehyde, a ketone, a sulphonate, a thioate, adisulphide, a xanthate, an amine, a pyridine, a hydrazide, a phenoxide,an alcohol with a boiling point above 100° C., or a derivative thereof,under substitution conditions whereby a proportion of the leaving groupsare substituted to form a substituted precursor copolymer comprisingunits of general formula ArCHR¹—CR²L_(m)ArCHR¹—CR²X_(l), in whichAr, R¹, R² and L are as defined above, X is a substituent group from thereactant, l and m are independently integers; and

(3) converting the substituted precursor copolymer to a conjugatedpoly(arylene vinylene) copolymer by elimination of the leaving groupsfrom the substituted precursor copolymer.

Throughout this specification, the term arylene is intended to includein its scope all types of arylenes including heteroarylenes as well asarylenes incorporating more than one ring structure, including fusedring structures. Ar may be paraphenylene, 1,4 naphthylene, 1,4anthracene, 2,6 fluorene and is preferably paraphenylene.

R¹ and R² may be independently selected from C₁-C₁₀ alkyl, C₁-C₁₀alkoxy, aryl such as substituted or unsubstituted phenyl, heterocyclicor polycyclic aryl, —CN or —CF₃. Preferably both R¹ and R² are H.

Where the reactant comprises a carboxylate, a carboxylate salt ispreferred. In this way, the precursor polymer may be made conventionallysuch as by base-catalysed polymerisation from suitable monomers such asparaxylylene bis(tetrahydrothiophenium bromide). The carboxylate salt isthen added to the precursor polymer. Other suitable monomers aredescribed in U.S. Pat. No. 5,401,827.

Advantageously, the precursor polymer may be provided by base-catalysedpolymerisation from suitable monomers in a molar excess of base. In thisway, the carboxylate salt is formed by neutralisation of the base withits corresponding carboxylic acid. One advantage of this method is thatit can be carried out in a single reaction zone such as a suitablecontainer, in which the precursor polymer is formed in the excess baseand, after polymerisation is complete, neutralisation takes place so asto form the substituted precursor copolymer prior to conversion into theconjugated poly(arylene vinylene) copolymer.

The carboxylate may be aliphatic such as formate or acetate and may beformed by the corresponding aliphatic carboxylic acids, formic acid oracetic acid. Substituted or unsubstituted aromatic carboxylates may beused such as those formed from 2,6 dimethylbenzoic acid, as well asderivatives thereof.

Materials of the following general formulae may be used:

R′—CO₂H or Ar′—CO₂H,

where R′=(cyclo)alkyl chain, Ar′=substituted or unsubstituted aromaticor polycyclic system.

In a further embodiment of this invention the substitution approach maybe facilitated by the interaction of precursor polymer with a basicsolution of a ketone or aldehyde (ie carbonyl) based system. Typicalcarbonyl based systems have the general structure shown and wouldinclude benzaldehyde, anthraldehyde, and benzophenone:

R³R⁴C=O or R³HC=O,

in which R³ and R⁴ are each independently R′ or Ar′ as defined above.

In a further embodiment of this invention oxygen, sulphur and nitrogennucleophiles may be used to form PPV precursor copolymers. A two-stagesynthesis involves precursor polymer preparation followed by treatmentwith alcohols or alkoxides, thiols or thiolates, or amines( for examplediphenylamine) etc. Following this the solution must be neutralised inthe normal way using an inorganic acid such as HCl or HBr or by usingone of the carboxylic acids listed above.

Oxygen nucleophiles would include sulphonic acids, phenoxide, alcohols,and derivatives thereof. Where alcohols are used they should have a lowvolatility so that, under thermal conversion to form conjugatedcopolymer, significant loss of alcohol does not occur.

Sulphur-containing nucleophiles would also include thioacids,disulphides, xanthates, and derivatives thereof.

Nitrogen nucleophiles would include primary, secondary, and tertiaryaliphatic or aromatic amines, pyridines, hydrazides, and derivativesthereof.

Converting step (3) is generally carried out at a temperature in therange 80° C. to 350° C., usually around 150° C. at a time in the range30 minutes to 10 hours, preferably around 4 hours. The process accordingto the present invention may involve treating the precursor polymer,either before or after purification, with suitable reagents, or carryingout the polymerisation in the presence of such reagents.

Substituent group X is formed from the substitution reaction between thereactant and the precursor polymer, for example by nucleophilicsubstitution. The reactant may be chosen to produce group X asachemically beneficial moiety to be incorporated into the vinylcopolymer. Thus, group X may be capable of chelating or binding indiumor other undesirable impurities such as catalyst residues. Examples ofsuch reactants would include acetyl acetone or 8-hydroxyquinoline.Alternatively, copolymers may be prepared with cross-linkable groups.Such groups would be capable of cross-linking to another part of theconjugated poly(arylene vinylene) copolymer or to another polymer chainsuch as another chain of the poly(arylene vinylene) copolymer. In thiscase, substitutent group X would include acrylates and cinnamates and beintroduced into the polymer by neutralising the polymerisation solutionwith acrylic acid or cinnamic acid respectively. The level ofincorporation would be determined by the amount of base used for thepolymerisation.

In a further aspect of this invention, a low band gap lumophore orchromophore may be incorporated into the copolymer by nucleophilicdisplacement of the leaving group to yield a semiconductive copolymercontaining lower band gap lumophores as compared to the copolymer.Exciton migration to the lower band gap component leads to efficientemission from the lumophore with the corresponding shift in emissionspectrum Hence, this method may be used to tune the emission orabsorption characteristics of PPV.

An important aspect of the present process is that the concentration ofnon-conjugated segments in the final copolymer may be increased to sucha level that the emission spectrum is significantly blue shifted. In theextreme, blue emission is observed. This method therefore provides ahighly controllable way in which to tune the emission from poly(arylenevinylene) copolymers such as PPV copolymers.

In a further aspect, there is provided a process for the production of aluminescent device comprising a conjugated poly(arylene vinylene)copolymer supported on a substrate, which process comprises preparing aconjugated poly(arylene vinylene) copolymer in accordance with the aboveprocess wherein converting step (3) is carried out on the substrate.

In a further aspect, there is provided a process for the production ofan electroluminescent device comprising a first electrode, a secondelectrode and at least one layer between the electrodes, including aconjugated poly(arylene vinylene) copolymer layer, which processcomprises preparing a conjugated poly(arylene vinylene) copolymer inaccordance with the above process, wherein converting step (3) iscarried out on the first electrode.

The first electrode may comprise a conductive oxide such as indium tinoxide, aluminium-doped zinc oxide, fluorine-doped tin oxide, vanadiumoxide, molybdenum oxide, nickel oxide; a conducting polymer; or a metalfilm.

In accordance with this invention, the poly(arylene vinylene) copolymersexhibit high photoluminescent efficiencies in the presence or absence ofconductive oxide substrates such as indium tin oxide.

According to another aspect of the invention there is provided amultilayer electroluminescent device of high electroluminescenceefficiency, incorporating a converted precursor copolymer as theemitting layer and an underlying electrode on which the conversionprocess has been carried out. At least one other layer is present one ofwhich is the second electrode. The emissive copolymer exhibits enhancedphotoluminescence efficiency in the presence or absence of ITO, enhancedEL efficiency and differential stability during device driving.

EL device manufacture is typically carried out by coating of theprecursor copolymer by suitable means usually at a thickness of around100 nm onto, for example, a semi-transparent conductive oxide. Theprecursor copolymer film is then converted to form the semiconductiveconjugated copolymer. Following this, a suitable metal electrode isdeposited and, following the application of a suitable voltage, lightemission is observed.

The semiconductive conjugated poly(arylene vinylene) copolymers of thepresent invention may be used as charge transport layers or chargeinjection layers or light emitting layers in luminescent devices,especially electroluminescent devices including optically orelectrically pumped lasers. The polymers may also be used as polymericfluorescent dyes.

The present invention will now be described in further detail, by way ofexample only, with reference to the following Examples an heaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in outline a standard precursor approach to the productionof PPV;

FIG. 2 shows a typical structure for an electroluminescent device; and

FIG. 3 shows a reaction scheme in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1

A specific embodiment is now described, see Table 1. One a equivalent(6.2 g) of p-xylylene bis(tetrahydrothiophenium bromide) is taken anddissolved in 120 ml 50/50 water/methanol solvent mixture. The solutionis then deoxygenated for at least 20 mins with a nitrogen purge.Following this a deoxygenated solution of 5 equivalents of potassiumhydroxide in 20 ml 50/50 water methanol is added to the monomersolution. When the polymerisation is complete neutralisation is carriedout with 10 ml acetic acid. The product is then dialysed against 50/50water/methanol until the dialate conductivity is <1 μS/cm. The finaldialysis is then carried out against neat methanol. The product, whichcontains ˜40 mol %. of the acetate function may now be used for thefabrication of an EL device as described below.

EXAMPLE 2

In a further specific embodiment, the proportion of acetatefunctionality may be altered by carrying out the synthesis as in Example1 but using 1, 2.5 or 10 equivalents of base used for the polymerisationand then using respectively 0.9, 5 and 20 ml of acetic acid required forneutralisation. As the number of equivalents of base used for thepolymerisation increases, and therefore the amount of acetate availablefor substitution increases, so does the acetate concentration increasein the final polymer.

EXAMPLE 3

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in150 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 20 equivalents of potassium hydroxide in 80ml 50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 80 mlacetic acid. The product is then dialysed against 50/50 water/methanoluntil the dialate conductivity is <1 μS/cm. The final dialysis is thencarried out against neat methanol.

EXAMPLE 4

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in200 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 30 mins with a nitrogen purge. Following thisa deoxygenated solution of 40 equivalents of potassium hydroxide in 160ml 50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 40 mlacetic acid. The product is then dialysed against 50/50 water/methanoluntil the dialate conductivity is <1 μS/cm. The final dialysis is thencarried out against neat methanol.

EXAMPLE 5

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 8 mlformic acid. The product is then dialysed against 50/50 water/methanoluntil the dialate conductivity is <1 μS/cm. The final dialysis is thencarried out against neat methanol. The product may now be used for thefabrication of an EL device as described below.

EXAMPLE 6

In a further specific embodiment, the proportion of formatefunctionality may be altered by carrying out the synthesis as in Example5 but using 1, 2.5 or 10 equivalents of base used for the polymerisationand and then using respectively 0.8, 4 and 16 ml of formic acid requiredfor neutralisation. As the number of equivalents of base used for thepolymerisation increases , and therefore the amount of formate availablefor substitution increases, so does the formate concentration increasein the final polymer.

EXAMPLE 7

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in150 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 20 equivalents of potassium hydroxide in 80ml 50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 26 mlformic acid. The product is then dialysed against 50/50 water/methanoluntil the dialate conductivity is <2 μS/cm. The final dialysis is thencarried out against neat methanol. The product may now be used for thefabrication of an EL device as described below.

EXAMPLE 8

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in200 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 40 equivalents of potassium hydroxide in 160ml 50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 56 mlformic acid. The product is then dialysed against 50/50 water/methanoluntil the dialate conductivity is <2 μS/cm. The final dialysis is thencarried out against neat methanol. The product may now be used for thefabrication of an EL device as described below.

EXAMPLE 9

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in220 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 80 equivalents of potassium hydroxide in 240ml 50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 112 mlformic acid. The product is then dialysed against 50/50 water/methanoluntil the dialate conductivity is <2 μS/cm. The final dialysis is thencarried out against neat methanol. The product may now be used for thefabrication of an EL device as described below.

EXAMPLE 10

Another specific embodiment is now described. A quantity of preformedPPV precursor (homopolymer or copolymer purified by dialysis) is takenand treated with a solution of 0.1-100 equivalents of a suitable saltsystem that yields approporiate nucleophilic species on dissolution.Examples of the salt would include sodium acetate, tetrabutyl ammoniumacrylate, tetrabutyl ammonium cinnamate, tetrabutyl ammonium benzoate,tetrabutyl ammonium thiolacetate, sodium formate, sodium phenolate etc.The precursor polymer solution is treated with the salt solution for upto 24 hours or until the required level of substitution is obtained.Purification is then carried out by dialysis. The preformed homopolymerPPV may be synthesised in situ.

EXAMPLE 11

Another specific embodiment is now described. A quantity of preformedPPV precursor homopolymer is taken and treated with a solution of 25equivalents of sodium acetate. The precursor polymer solution is treatedwith the salt solution for up to 11 hours or until the required level ofsubstitution is obtained. Purification is then carried out by dialysis.

EXAMPLE 12

In a further specific embodiment, the proportion of acetatefunctionality may be altered by carrying out the synthesis as in Example11 but using 12.2, 40, 100 and 200 equivalents of sodium acetate.

EXAMPLE 13

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is then for atleast 20 mins with a nitrogen purge. Following this a deoxygenatedsolution of 5 equivalents of potassium hydroxide and 20 equivalents ofpotassium acetate in 100 ml 50/50 water methanol is added to the monomersolution. When the polymerisation is complete neutralisation is carriedout with 10 ml acetic acid. The product is then dialysed against 50/50water/methanol until the dialate conductivity is <1 μS/cm. The finaldialysis is then carried out against neat methanol. The product may nowbe used for the fabrication of an EL device as described below.

EXAMPLE 14

In a further specific embodiment, the proportion of acetatefunctionality may be altered by carrying out the synthesis as in Example13 but using 10 or 40 equivalents of sodium acetate.

EXAMPLE 15

Another specific embodiment is now described. One equivalent 6.2g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is then for atleast 20 mins with a nitrogen purge. Following this a deoxygenatedsolution of 5 equivalents of potassium hydroxide in 20 ml 50/50water/methanol. When the polymerisation is complete neutralisation iscarried out with 10 ml acetic acid hydroxide and 20 equivalents ofpotassium acetate in 50 ml 50/50 water methanol. The product is thendialysed against 50/50 water/methanol until the dialate conductivity is<1 μS/cm. The final dialysis is then carried out against neat methanol.The product may now be used for the fabrication of an EL device asdescribed below.

EXAMPLE 16

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added slowly to the monomer solution.Simultaneusly, 5 equivalents of phenol are added dropwise and thesolution is allowed to stir for 2 mins. When the polymerisation iscomplete neutralisation is carried out with 10 ml acetic acid or 20 mlHCl. The product is then dialysed against 50/50 water/methanol until thedialate conductivity is <1 μS/cm. The final dialysis is then carried outagainst neat methanol. The product may now be used for the fabricationof an EL device as described below.

EXAMPLE 17

In a further specific embodiment, the proportion of phenolatefunctionality may be increased by carrying out the synthesis as inExample 10 but using 1 or 10 equivalents of phenol. As the number ofequivalents of phenol increases phenol concentration increase in thefinal polymer.

EXAMPLE 18

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in140 ml 57/43 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete 1 equivalent of picric acid i.e.45 mlsolution (3.4 M in water) are added and the solution is allowed to stirfor 2 mins. Neutralisation is then carried out with 10 ml acetic acid.The product is then dialysed against 50/50 water/methanol until thedialate conductivity is <1 μS/cm. The final dialysis is then carried outagainst neat methanol. The product may now be used for the fabricationof an EL device as described below.

EXAMPLE 19

Another specific embodiment is now described. One equivalent (1.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) was prepared in situ byallowing to react one equivalent of α, α-dibromo-p-xylene with 2equivalents of tetrahydrothiophene in 10 ml of deoxygenated methanol for16 h at 55° C. under nitrogen. 20 ml of water and 10 ml of methanol werethen added. The solution is then deoxygenated for at least 20 mins witha nitrogen purge. Following this a deoxygenated solution of 5equivalents of potassium hydroxide in 10 ml 50/50 water methanol isadded to the monomer solution. When the polymerisation is completeneutralisation is carried out with 5.1 equivalents of 2,6 dimethylbenoic acid. The product is then dialysed once against 51 of 50/50 watermethanol and then 3 times against 5 liters of neat methanol. The productmay now be used for the fabrication of an EL device as described below.

EXAMPLE 20

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete 0.25 equivalents of diphenyl amine are addedand the solution is allowed to stir for 1.5 mins. Neutralisation is thencarried out with 10 ml acetic acid or 20 ml HCL. The product is thendialysed against 50/50 a water/methanol until the dialate conductivityis <1 μS/cm. The final dialysis is then carried out against neatmethanol. The product may now be used for the fabrication of an ELdevice as described below.

EXAMPLE 21

Another specific embodiment is now described. A quantity of preformedPPV precursor acetate copolymer is taken and treated with 0.25equivalents of diphenyl amine (10 mg). The solution was stirred at roomtemperature for 30 min. Purification by dialysis is not needed.

EXAMPLE 22

Another specific embodiment is now described. A quantity of preformedPPV precursor acetate copolymer is taken and treated with 0.7equivalents of diphenyl amine (27 mg). Purification was carried out bydialysis against 21 of neat methanol.

EXAMPLE 23

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 12 ml ofmethane sulfonic acid. The product is then dialysed against 50/50water/methanol until the dialate conductivity is <5 μS/cm. The finaldialysis is then carried out against neat methanol. The product may nowbe used for the fabrication of an EL device as described below.

EXAMPLE 24

In a further specific embodiment, the proportion of methanesulfonatefunctionality may be increased by carrying out the synthesis as inExample 23 but using 10 equivalents of base used for the polymerisationand and then increasing proportionally the amount of methane sulfonicacid required for neutralisation.

EXAMPLE 25

Another specific embodiment is now described. One equivalent (3.1 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in75 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 20 equivalents of potassium hydroxide in 40ml 50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 24 ml ofmethane sulfonic acid. The product is then dialysed against 50/50water/methanol until the dialate conductivity is <2 μS/cm. The finaldialysis is then carried out against neat methanol. The product may nowbe used for the fabrication of an EL device as described below.

EXAMPLE 26

Another specific embodiment is now described. A preformed and purifiedprecursor polymer solution is taken and treated with 0.25 eqs of methanesulphonic acid. The solution is stirred overnight (16 hrs) and followingthis a sulphonate based PPV copolymer is obtained and is ready forfabrication into an EL device as described below or a furtherpurification step may be required.

EXAMPLE 27

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 100 ml of0.01 M sulfuric acid. The product is then dialysed against 50/50water/methanol until the dialate conductivity is <1 μS/cm. The finaldialysis is then carried out against neat methanol. The product may nowbe used for the fabrication of an EL device as described below.

EXAMPLE 28

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete 1 equivalent of hydroxy coumarin slurry in 27ml of methanol are added and the solution is allowed to stir for 2 mins.Neutralisation is then carried out with 10 ml acetic acid or 20 ml HCl.The product is then dialysed against 50/50 water/methanol until thedialate conductivity is <2 μS/cm. The final dialysis is then carried outagainst neat methanol. The product may now be used for the fabricationof an EL device as described below.

EXAMPLE 29

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete 1 equivalent of benzaldehyde are added andthe solution is allowed to stir for 2 mins. Neutralisation is thencarried out with 10 ml acetic acid or 20 ml HCl. The product is thendialysed against 50/50 water/methanol until the dialate conductivity is<1 μS/cm. The final dialysis is then carried out against neat methanol.The product may now be used for the fabrication of an EL device asdescribed below.

EXAMPLE 30

In a further specific embodiment, the proportion of carbonyl may beincreased by carrying out the synthesis as in Example 29 but using 0.33or 2 equivalents of benzaldehyde used.

EXAMPLE 31

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in140 ml 33/67 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 40 ml12/88 water methanol is added to the monomer solution. When thepolymerisation is complete 1.3 equivalent of benzophenone are added in70 ml methanol and the solution is allowed to stir for 20 seconds.Neutralisation is then carried out with 10 ml acetic acid. The productis then dialysed against 50/50 water/methanol until the dialateconductivity is <1 μS/cm. The final dialysis is then carried out againstneat methanol. The product may now be used for the fabrication of an ELdevice as described below.

EXAMPLE 32

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete 0.03 equivalents of antracene aldehydedissolved in 30 ml of methanol are added and the solution is allowed tostir for 2 mins. Neutralisation is then carried out with 10 ml aceticacid. The product is then dialysed against 50/50 water/methanol untilthe dialate conductivity is <1 μS/cm. The final dialysis is then carriedout twice against neat methanol. The product may now be used for thefabrication of an EL device as described below.

EXAMPLE 33

Another specific embodiment is now described. A quantity of preformedPPV precursor acetate copolymer is taken and treated with a solution of0.14 equivalents of antracene aldehyde. Purification is carried out bydialysis.

EXAMPLE 34

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete 5 equivalents of acetylacetone dissolved in30 ml of methanol are added and the solution is allowed to stir for 2.5mins. Neutralisation is then carried out with 3 ml acetic acid. Theproduct is then dialysed against 50/50 water/methanol until the dialateconductivity is <1 μS/cm. The final dialysis is then carried out againstneat methanol. The product may now be used for the fabrication of an ELdevice as described below.

EXAMPLE 35

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete 5 equivalents of 3, methyl, 2,4 pentanedionedissolved in 30 ml of methanol are added and the solution is allowed tostir for 2.5 mins. The product is then dialysed against 50/50water/methanol until the dialate conductivity is <1 μS/cm. The finaldialysis is then carried out against neat methanol. The product may nowbe used for the fabrication of an EL device as described below.

EXAMPLE 36

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 20 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 12 mlacrylic acid. The product is then dialysed against 50/50 water/methanoluntil the dialate conductivity is <1 μS/cm. The final dialysis is thencarried out against neat methanol. The product may now be used for thefabrication of an EL device as described below.

EXAMPLE 37

In a further specific embodiment, the proportion of acrylatefunctionality may be altered by carrying out the synthesis as in Example36 but using 10 equivalents of base used for the polymerisation and andthen using respectively 24 ml of acrylic acid for neutralisation. As thenumber of equivalents of base used for the polymerisation increases, andtherefore the amount of acrylate available for substitution increases,so does the acrylate concentration increase in the final polymer.

EXAMPLE 38

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in150 ml 50/50 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 20 equivalents of potassium hydroxide in 80ml 50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 45.7 mlacrylic acid. The product is then dialysed against 50/50 water/methanoluntil the dialate conductivity is <1 μS/cm. The final dialysis is thencarried out against neat methanol. The product may now be used for thefabrication of an EL device as described below.

EXAMPLE 39

Another specific embodiment is now described. A quantity of preformedPPV precursor homopolymer is taken and treated with a solution of 25equivalents of an acrylate salt. The precursor polymer solution istreated at room temperature with the salt solution for up to 11 hours oruntil the required level of substitution is obtained. Purification isthen carried out by dialysis.

EXAMPLE 40

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in120 ml 50/50 water/methanol solvent mixture. The solution is then for atleast 20 mins with a nitrogen purge. Following this a deoxygenatedsolution of 1 equivalents of potassium hydroxide in 4 ml 50/50 watermethanol is added to the monomer solution. When the polymerisation iscomplete a deoxygenated solution of 9 equivalents of potassim acrylateand 1 equivalent of acrylic acid in 50 ml 50/50 water/methanol is added.The product is then dialysed against 50/50 water/methanol until thedialate conductivity is <1 μS/cm. The final dialysis is then carried outagainst neat methanol. The product may now be used for the fabricationof an EL device as described below.

EXAMPLE 41

In a further specific embodiment, the proportion of acrylatefunctionality may be increased by carrying out the synthesis as inExample 40 but using 19 equivalents of potassium acrylate. As the numberof equivalents of acrylate increases acrylate concentration increase inthe final polymer.

EXAMPLE 42

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in180 ml 33/67 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide in 40 ml50/50 water methanol is added to the monomer solution. When thepolymerisation is complete neutralisation is carried out with 5.8equivalents of cinnamic acid dissolved in 120 ml of methanol. Theproduct is then dialysed once against mrthanol then against 50/50water/methanol until the dialate conductivity is <1 μS/cm. The finaldialysis is then carried out against neat methanol. The product may nowbe used for the fabrication of an EL device as described below.

EXAMPLE 43

Another specific embodiment is now described. One equivalent (6.2 g) ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in180 ml 33/67 water/methanol solvent mixture. The solution is then for atleast 20 mins with a nitrogen purge. Following this a deoxygenatedsolution of 5 equivalents of potassium hydroxide and 20 equivalents ofpotassium cinnamate in 160 ml 12/88 water methanol is added to themonomer solution. When the polymerisation is complete neutralisation iscarried out with 5.0 equivalents of cinnamic acid dissolved in 100 ml ofmethanol. The produce is then dialysed against 50/50 water/methanoluntil the dialate conductivity is <1 μS/cm. The final dialysis is thencarried out against neat methanol. The product may now be used for thefabrication of an EL device as described below.

EXAMPLE 44

Another specific embodiment is now described. A quantity of preformedPPV precursor homopolymer is taken and treated with a solution of 25equivalents of an cinnamate salt. The precursor polymer solution istreated with the salt solution for up to 10 hours or until the requiredlevel of substitution is obtained. Purification is then carried out bydialysis.

EXAMPLE 45

Another specific embodiment is now described. One equivalent ofp-xylylene bis(tetrahydrothiophenium bromide) is taken and dissolved in160 ml 37/63 water/methanol solvent mixture. The solution is thendeoxygenated for at least 20 mins with a nitrogen purge. Following thisa deoxygenated solution of 5 equivalents of potassium hydroxide and 1equivalent of 8-hydroxyquinoline in 70 ml 15/85 water methanol is addedto the monomer solution. When the polymerisation is completeneutralisation is then carried out with 10 ml acetic acid. The productis then dialysed against 50/50 water/methanol until the dialateconductivity is <1 μS/cm. The final dialysis is then carried out againstneat methanol. The product may now be used for the fabrication of an ELdevice as described below.

EXAMPLE 46

Another specific embodiment is now described. One equivalent ofpreformed acetate copolymer is mixed with 29.5 equivalents of glyceroland 51.3 equivalents of diethylene glycol. Coat by suitable means theprecursor PPV solution at a thickness of 100 nm (after conversion) ontoa semi-transparent conductive oxide. The precursor PPV copolymer film isthen converted at 150° C. for 4 hours under nitrogen. The product maynow be used for the fabrication of an EL device after a suitable metalelectrode is deposited as described below.

EXAMPLE 47

Referring to FIG. 2, device manufacture is carried out by coating byspin-coating the substituted precursor copolymer at a thickness of 100nm after conversion onto a semi-transparent indium tin oxide layer 2 ona glass substrate 1. The precursor copolymer film 3 is then converted a150° C. for 4 hours. Following this, a calcium electrode 6 is depositedby thermal evaporation and, following the application of a suitablevoltage (5V), light emission is observed. Additional polymer layers 3and 5 may be applied during manufacture of the device to act as chargetransport layers.

TABLE 1 PL efficency BrPPV KOH:A A:S (%) monomer solvent Temp. mol. KOHSubstituant mol. amount on Glass/ (A) W-MeOH ° C. ratio conc. (S) Typeratio Neutralising acid of acid 100 a/n on ITO 6.2 g 120 ml 20 5 3.75Mnone le homopolymer — HCl (10 N) 10 ml −20  10/1.5 6.2 g 120 ml 20 53.75M acetate I — Acetic Ac. (glacial) 10 ml — 55/2  6.2 g 120 ml 20 10 7.5M acetate I — Acetic Ac. (glacial) 20 ml — 57/20 6.2 g 150 ml 12 203.75M acetate I — Acetic Ac. (glacial) 40 ml — 57/29 6.2 g 200 ml 12 403.75M acetate I — Acetic Ac. (glacial) 80 ml — 50/30 6.2 g 120 ml 20 53.75M formate I — Formic Ac. (99%) 7 ml — 40/2* 6.2 g 150 ml 12 20 3.75Mformate I — Formic Ac. (99%) 30 ml —  55/27* 2.1 g  40 ml 20 5  2.5Mdimethylbenzoate I — dimethylbenzoic acid 3.7 g —  59/22* 6.2 g 120 ml20 5 3.75M phenolate II 1:1 Acetic Ac. (glacial) 10 ml —  62/29* 6.2 g120 ml 20 5 3.75M phenolate II 1:5 Acetic Ac. (glacial) 10 ml —  62/38*6.2 g 120 ml 20 5 3.75M methanesulfonate II — Methane sulfonic acid 12ml —   10/1.5* 3.1 g  75 ml 12 20 3.75M methanesulfonate II — Methanesulfonic acid 24 ml — 14/2* 6.2 g 120 ml 20 5 3.75M sulfonate II —Sulfuric Ac. (0.01 M) 100 ml —   10/1.5* 6.2 g 120 ml 20 5 3.75Mcoumarin oxyde II 1:1 Acetic Ac. (glacial) 10 ml —  45/18* 6.2 g 120 ml20 5 3.75M diphenylamine II 3:1 Acetic Ac. (glacial) 10 ml — 48/2* 6.2 g120 ml 20 5 3.75M diphenylamine II 1:1 Acetic Ac. (glacial) 10 ml —54/4* 6.2 g 120 ml 20 5 3.75M benzaldehyde III 3:1 Acetic Ac. (glacial)10 ml —  60/32* 6.2 g 120 ml 20 5 3.75M benzaldehyde III 1:1 Acetic Ac.(glacial) 10 ml —  65/37* 6.2 g 120 ml 20 5 3.75M benzaldehyde III 1:1HCl (10 N) 20 ml — 18/2* 6.2 g 120 ml 20 5 3.75M benzaldehyde III 1:2HCl (10 N) 20 ml — 50/4* 6.2 g 120 ml 20 5 3.75M anthracenealdehyde III7:1 Acetic Ac. (glacial) 10 ml — 55/3* 6.2 g 120 ml 20 5 3.75Macetylacetonate IV 1:5 Acetic Ac. (glacial) 3 ml —  50/18* 6.2 g 150 ml12 20 3.75M aceylate V — Acrylic Ac. (99%) 47 ml —  55/30* Type I:carboxylate; Type II: O,S,N nucleophiles; Type III: carbonyles; Type IV:miscellaneous; Type V: crosslinking. *: Indirect measurement carried outusing a calibration curve.

What is claimed is:
 1. A process for the preparation of a conjugatedpoly(arylene vinylene) copolymer for use in a luminescent device, whichcomprises: (1) providing a precursor polymer comprising units of generalformula (—Ar CHR¹—CR²L—)_(n), in which Ar is substituted orunsubstituted arylene, L is a leaving group, R¹ and R² are eachindependently selected from the group consisting of H, alkyl, alkoxy,aryl and an electron-withdrawing group, and n is an integer; (2)reacting the precursor polymer with a reactant comprising a residueselected from the group consisting of a carboxylate, an aldehyde, aketone, an amine, and a derivative thereof, under substitutionconditions whereby a proportion of the leaving groups are substituted toform a substituted precursor copolymer comprising units of generalformula (—Ar CHR¹—CR²L—)_(m)(—Ar CHR¹—CR²X—)_(l), in which Ar, R¹, R²and L are as defined above, X is a substituent group from the reactant,l and m are independently integers; and (3) converting the substitutedprecursor copolymer to a conjugate poly(arylene vinylene) copolymer byelimination of the leaving groups from the substituted-precursorcopolymer.
 2. A process according to claim 1, wherein R¹ and R² are bothH.
 3. A process according to claim 1 or claim 2, wherein the reactantcomprises a carboxylate salt.
 4. A process according to claim 3, whereinthe precursor polymer is provided by base-catalysed polymerisation fromsuitable monomers and the carboxylate salt is added to the precursorpolymer.
 5. A process according to claim 3, wherein the precursorpolymer is provided by base-catalysed polymerisation from suitablemonomers in a molar excess of base and the carboxylate salt is formed byneutralisation of the base with the corresponding carboxylic acid.
 6. Aprocess according to claim 1 or claim 2, wherein the carboxylate isC₁-C₁₀ aliphatic.
 7. A process according to claim 6, wherein thealiphatic carboxylate is formate or acetate.
 8. A process according toclaim 1 or claim 2, wherein the carboxylate is aromatic.
 9. A processaccording to claim 8, wherein the aromatic carboxylate is 2,6-dimethylbenzoate.
 10. A process according to claim 1 or claim 2, wherein thereactant comprises a basic solution of a compound selected from thegroup consisting of an aldehyde and a ketone.
 11. A process according toclaim 10, wherein the aldehyde or ketone is selected from the groupconsisting of benzaldehyde, anthraldehyde and benzophenone.
 12. Aprocess according to claim 1 or claim 2, wherein group X is capable ofchelating or binding indium.
 13. A process according to claim 12,wherein the reactant comprises a compound selected from the groupconsisting of acetyl acetone and 8-hydroxyquinoline.
 14. A processaccording to claim 1 or claim 2, wherein the group X comprises alumophore.
 15. A process according to claim 1 or claim 2, wherein groupX is capable of cross-linking to another part of the conjugatedpoly(arylene vinylene) copolymer or to another polymer chain.
 16. Aprocess according to claim 15, wherein the reactant to form group X isan acrylate or a cinnamate.
 17. A process according to claim 1 or claim2, wherein Ar is p-phenylene.
 18. A process for the production of aluminescent device comprising a conjugated poly(arylene vinylene)copolymer supported on a substrate, which process comprises preparing aconjugated poly(arylene vinylene) copolymer in accordance with theprocess of claim 1 or claim 2 wherein converting step (3) is carried outon the substrate.
 19. A process for the production of anelectroluminescent device comprising a first electrode, a secondelectrode and at least one layer between the electrodes, including aconjugated poly(arylene vinylene) copolymer layer, which processcomprises preparing a conjugated poly(arylene vinylene) copolymer inaccordance with the process of claim 1 or claim 2, wherein convertingstep (3) is carried out on the first electrode.
 20. A process accordingto claim 19, wherein the first electrode comprises a conductive metaloxide.
 21. A conjugated poly(arylene vinylene) copolymer for use in aluminescent device, which is obtained by a process according to claim 1or claim
 2. 22. A luminescent device obtained from a process accordingto claim
 18. 23. An electroluminescent device obtained from a processaccording to claim
 19. 24. An electroluminescent device obtained from aprocess according to claim 20.